OFFSET
0,5
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..500
Wikipedia, Partition of a set
EXAMPLE
a(4) = 4: 123|4, 12|34, 14|23, 1|234.
MAPLE
b:= proc(n, x, y) option remember; convert(series(
`if`(n=0, 1, `if`(y=0, 0, expand(b(n-1, y-1, x+1)*y*z))
+b(n-1, y, x)*x + b(n-1, y, x+1)), z, 3), polynom)
end:
a:= n-> coeff(b(n, 0$2), z, 2):
seq(a(n), n=0..27);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Jun 10 2023
STATUS
approved